Mounting negatives as slides?

[FishyFish]

I recently acquired a big batch of old 35mm slides dating from the 60s to the 80s. The collection includes lots of Kodachromes, plus a variety of other tranparency emulsions in a variety of mounts. In amongst the ones I've looked at so far I've found a few mounts that appear to contain negatives rather than positive images. I'm curious as to whether there was a particular reason for someone to mount a negative in this way?

 

[StephenM]

I've never come across this, but a few possible reasons spring to mind.

Use the projector as a cheap/free horizontal enlarger;

Preferring to not risk scratches from pulling a 35mm strip through a conventional enlarger;

Negative storage that integrates with the slide storage system (someone who uses little negative film);

A means of keeping special or important negatives separate from the rest.

 

[JackBell]

My father used to do this, he shot mainly slide film and mounted his own slides. He was very strict with the images he kept, maybe only one or two from a 36 exp roll or sometimes none. Any negative film shot that was deemed to be a keeper was mounted in a slide, all other slides/negs were binned.

 

[Harlequin565]

Or is it for when you use a Reversal Bulb in the projector?

 

[FishyFish]

Or is it for when you use a Reversal Bulb in the projector?

My initial thoughts were more along the lines of if you look through the slide from the wrong side then it will show a properly reversed image.